Under a bright morning sun, engineers and soldiers started erecting long iron pickets from Nathu La to Sebu La while 2 Grenadiers and Artillery Observation Post Officers at Sebu La and Camel's Back were on alert. Immediately, the Chinese commissar came to the centre of the Pass.
The commissar asked Lt. Col. Rai Singh to stop laying the wire. Orders to the Indian Army were clear. They were not to blink. An argument soon built up into a scuffle. In the melee, the commissar got roughed up. Thereafter the Chinese went back to their bunkers. Engineers resumed laying the wire.
Within minutes, a whistle was heard on the Chinese side followed by murderous medium machine gun fire. Jawans of 70 Field Company and 18 Rajput were caught in the open and suffered heavy casualties.
Col Rai Singh was wounded. Two brave officers, Capt Dagar of 2 Grenadiers and Major Harbhajan Singh of 18 Rajput, rallied a few troops and tried to assault the Chinese MMG but both died a heroic death.